Stabilities of substituted benzyl radicals: Dissociation rates of amino-, hydroxy-, and cyanoethylbenzenes

Journal Article · Thu Oct 19 04:00:00 EDT 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100358a023· OSTI ID:6825320

Suryan, M M; Stein, S E ^[1]

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1. National Institute of Standards and Technology, Gaithersburg, MD (USA)

Rates of the thermal unimolecular decomposition of amino-, hydroxy-, and cyanoethylbenzenes have been determined by the very low pressure pyrolysis technique. Assuming equal A factors, these rates, relative to the rate of dissociation of ethylbenzene, yield the following ortho, meta, and para, respectively, substituent effects on benzylic C-C bond strengths (kcal/mol): NH{sub 2}, {minus}2.7, {minus}0.3, {minus}1.7; OH, {minus}1.7, {minus}0.7, {minus}1.1; and CN, {minus}0.3, 0.4, {minus}1.5. These effects are generally smaller than those for substituted anisoles and follow different trends. Along with the results of ESR studies of Nicholas and Arnold (Can. J. Chem. 1986, 64, 270), the present substituent effects indicate that a 1-G change in the benzylic hyperfine coupling constant corresponds to a 1.8 kcal mol{sup {minus}1} change in bond strength.

• OSTI ID: 6825320
• Journal Information: Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 93:21; ISSN 0022-3654; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ARYL RADICALS
BENZYL RADICALS
CALCULATION METHODS
CHEMICAL REACTION KINETICS
DATA
DATA ANALYSIS
EXPERIMENTAL DATA
INFORMATION
KINETICS
LOW PRESSURE
MEASURING INSTRUMENTS
MEASURING METHODS
NUMERICAL DATA
PYROLYSIS PRODUCTS
RADICALS
REACTION KINETICS